Integrated circuit manufacturers routinely test integrated circuits for performance and quality. Testing may be performed solely for the benefit of the manufacturer or at the request of the customer and is an expense that is figured into the cost of integrated circuits.
Customers require that the testing procedure include temperature testing. A commercial customer may require that a device be tested for performance and quality in temperature extremes from 0 degrees Celsius to 70 degrees Celsius. A military customer may demand testing in a temperature range of -55 degrees Celsius to +125 degrees Celsius. In either case, the device under test must be placed in a temperature controlled environment during testing.
Presently, there are two routinely used methods to temperature control the environment of a device during testing. In the first method, a single device is tested using a commercially available temperature forcing unit to temperature control the environment of the device. For example, the device to be tested is connected to the performance board of an IC tester. A temperature forcing unit is placed over the device to provide an environment for the device that can be temperature controlled during testing. Present test times of 10-12 minutes for each device are common place. The problem for manufacturers is the negative impact on productivity that results from such lengthy test times for single devices.
The second method uses automated device handlers. Automated device handlers provide temperature controlled environments and automated loading and unloading mechanisms for the devices to be tested. The handlers accurately distribute conditioned air over a large area to multiple devices simultaneously. Connecting cables couple the handler to the tester. Since most testers can test more than one device at the same time, it is obviously more cost effective to test multiple devices simultaneously.
The advantages of a handler are its automation and its ability to accommodate more than one device at a time in its temperature controlled chamber. The disadvantages of a handler are: first, its cost, with some handlers costing hundreds of thousands of dollars each; second, most handlers are limited to the testing of one package type; and third, handlers do not exist for certain existing and new package designs. Moreover, low product volumes may not justify the purchase of a handler. Assuming that a manufacturer has a handler for a different package device, the time and expense of converting the handler to the new device, if possible, may also be prohibitive. Thus, the options available to the manufacturer are: test one device at a time with a temperature forcing unit; buy, a handler or convert one; or inform the customer that the manufacturer cannot adequately temperature test the devices.
What is needed is an efficient way to test multiple devices simultaneously over accurately controlled temperature ranges without the large capital expense associated with the purchase of an automated device handler.